Propagation of toroidal localized spoof surface plasmons using conductive coupling.

Here, on a platform of two split-ring resonator (SRR) disks in the microwave regime, we have numerically and experimentally investigated the coupling of toroidal localized spoof surface plasmons (LSSPs). The coupling effect is investigated both theoretically and experimentally. We observe that magnetic dipole coupling exists in the toroidal LSSPs coupling and causes a rearrangement of the toroidal LSSPs, which suppresses the propagation of toroidal LSSPs. To realize the propagation of toroidal LSSPs, we introduce conductive coupling into the SRR disks. The conductive coupling can correct magnetic dipole coupling and enhance toroidal LSSPs coupling. Both numerical simulations and experiments are in good agreement. The toroidal LSSPs can be effectively propagated, even in the three right-angle-bent SRR disks. This study paves the way toward a better understanding of toroidal LSSPs coupling and finds many applications in the transfer of electromagnetic energy using toroidal moments.